Johnson R E, Kovvali G K, Guzder S N, Amin N S, Holm C, Habraken Y, Sung P, Prakash L, Prakash S
Sealy Center for Molecular Science, University of Texas Medical Branch, Galveston, Texas 77555-1061, USA.
J Biol Chem. 1996 Nov 8;271(45):27987-90. doi: 10.1074/jbc.271.45.27987.
DNA mismatch repair plays a key role in the maintenance of genetic fidelity. Mutations in the human mismatch repair genes hMSH2, hMLH1, hPMS1, and hPMS2 are associated with hereditary nonpolyposis colorectal cancer. The proliferating cell nuclear antigen (PCNA) is essential for DNA replication, where it acts as a processivity factor. Here, we identify a point mutation, pol30-104, in the Saccharomyces cerevisiae POL30 gene encoding PCNA that increases the rate of instability of simple repetitive DNA sequences and raises the rate of spontaneous forward mutation. Epistasis analyses with mutations in mismatch repair genes MSH2, MLH1, and PMS1 suggest that the pol30-104 mutation impairs MSH2/MLH1/PMS1-dependent mismatch repair, consistent with the hypothesis that PCNA functions in mismatch repair. MSH2 functions in mismatch repair with either MSH3 or MSH6, and the MSH2-MSH3 and MSH2-MSH6 heterodimers have a role in the recognition of DNA mismatches. Consistent with the genetic data, we find specific interaction of PCNA with the MSH2-MSH3 heterodimer.
DNA错配修复在维持遗传保真度方面发挥着关键作用。人类错配修复基因hMSH2、hMLH1、hPMS1和hPMS2中的突变与遗传性非息肉病性结直肠癌相关。增殖细胞核抗原（PCNA）对于DNA复制至关重要，它在其中作为一种持续合成因子发挥作用。在此，我们在酿酒酵母中编码PCNA的POL30基因中鉴定出一个点突变pol30 - 104，该突变增加了简单重复DNA序列的不稳定性速率，并提高了自发正向突变的速率。对错配修复基因MSH2、MLH1和PMS1中的突变进行的上位性分析表明，pol30 - 104突变损害了MSH2/MLH1/PMS1依赖的错配修复，这与PCNA在错配修复中发挥作用的假设一致。MSH2与MSH3或MSH6一起在错配修复中发挥作用，并且MSH2 - MSH3和MSH2 - MSH6异二聚体在识别DNA错配方面发挥作用。与遗传数据一致，我们发现PCNA与MSH2 - MSH3异二聚体存在特异性相互作用。
